With the development of communication technologies, multiple types of services or traffic have been proposed, for example, enhanced mobile broadband (eMBB) generally requiring high data rate, massive machine type communication (mMTC) typically requiring long battery lifetime, and ultra-reliable and low latency communication (URLLC). Meanwhile, multi-antenna schemes, such as beam management, reference signal transmission, and so on, are studied for new radio access.
Conventionally, a network device (for example, an eNB or a gNB) transmits downlink reference signals (RSs) such as Demodulation Reference Signal (DMRS), Channel State Information-Reference Signal (CSI-RS), Sounding Reference Signal (SRS), and the like. A terminal device (for example, a user equipment) in the system may receive the downlink RSs on allocated resources. The terminal device may also transmit uplink RSs to the network device on corresponding allocated resources. For indicating the allocated resources for the RS s, the network device may transmit RS configurations to the terminal device prior to the transmissions of the RSs.
For example, two configuration patterns for DMRS have been designed and agreed in 3GPP specification works, each of which may support up to 8 or 12 orthogonal DMRS ports. This may result in a relatively large overhead for a network device to indicate a DMRS configuration to a terminal device. In this case, an overhead reduction scheme for DMRS configuration needs to be considered.